Conventional security systems typically include multiple motion detectors that are distributed throughout a home environment to be monitored for intrusions. For example, a home environment can be partitioned to include multiple zones. A corresponding motion detector in each zone (such as a room in a house, portion of a yard, etc.) monitors occurrences of motion.
Each of the zones of motion detectors is typically connected to a central controller of the security system that makes decisions about activating a respective alarm. Assuming that a security system is armed, in response to detecting motion in one of the multiple monitored zones, the security system activates the alarm to indicate presence of a moving object. Accordingly, the security system can detect and provide notification of detecting motion, which is presumably an intruder.
Conventional security systems are prone to false alarms. For example, a homeowner's dog may walk past a respective motion detector in a zone when the security system is armed. The respective motion detector may sense motion of the dog. In response to sensing the motion of the dog, the respective motion detector notifies the central controller that motion was detected. In response to the notification of the motion, the central controller activates the alarm. Thus, a non-intrusive event such as the motion of the dog can cause a false alarm.
Occurrence of false alarms is typically very undesirable. Many times, a security system is linked to communicate occurrences of detected motion events to a corresponding security agency at a remote location. Upon receiving notification of a motion event while the security system is armed, the security agency notifies authorities such as the police to investigate the detected motion, which is possibly an unlawful intrusion. As discussed above, a detected motion event may be harmless and caused by motion of a dog or other animal as opposed to motion caused by a burglar. When the homeowner's dog accidentally trips a motion detector, it is not desirable to dispatch police to investigate the event.
To address this issue, motion detector devices and/or a corresponding central controller sometimes include a filter circuit. During operation, the filter circuit analyzes a corresponding received motion signal to determine a size of a detected moving object. If an estimated size of the corresponding moving object is detected as being below a threshold value, the core controller may prevent activation of the alarm. Thus, to some extent false alarms can be prevented.